arch/s390/mm/maccess.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Access kernel memory without faulting -- s390 specific implementation.
   4  *
   5  * Copyright IBM Corp. 2009, 2015
   6  *
   7  *   Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
   8  *
   9  */
  10
  11 #include <linux/uaccess.h>
  12 #include <linux/kernel.h>
  13 #include <linux/types.h>
  14 #include <linux/errno.h>
  15 #include <linux/gfp.h>
  16 #include <linux/cpu.h>
  17 #include <asm/ctl_reg.h>
  18 #include <asm/io.h>
  19
  20 static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size)
  21 {
  22         unsigned long aligned, offset, count;
  23         char tmp[8];
  24
  25         aligned = (unsigned long) dst & ~7UL;
  26         offset = (unsigned long) dst & 7UL;
  27         size = min(8UL - offset, size);
  28         count = size - 1;
  29         asm volatile(
  30                 "       bras    1,0f\n"
  31                 "       mvc     0(1,%4),0(%5)\n"
  32                 "0:     mvc     0(8,%3),0(%0)\n"
  33                 "       ex      %1,0(1)\n"
  34                 "       lg      %1,0(%3)\n"
  35                 "       lra     %0,0(%0)\n"
  36                 "       sturg   %1,%0\n"
  37                 : "+&a" (aligned), "+&a" (count), "=m" (tmp)
  38                 : "a" (&tmp), "a" (&tmp[offset]), "a" (src)
  39                 : "cc", "memory", "1");
  40         return size;
  41 }
  42
  43 /*
  44  * s390_kernel_write - write to kernel memory bypassing DAT
  45  * @dst: destination address
  46  * @src: source address
  47  * @size: number of bytes to copy
  48  *
  49  * This function writes to kernel memory bypassing DAT and possible page table
  50  * write protection. It writes to the destination using the sturg instruction.
  51  * Therefore we have a read-modify-write sequence: the function reads eight
  52  * bytes from destination at an eight byte boundary, modifies the bytes
  53  * requested and writes the result back in a loop.
  54  *
  55  * Note: this means that this function may not be called concurrently on
  56  *       several cpus with overlapping words, since this may potentially
  57  *       cause data corruption.
  58  */
  59 void notrace s390_kernel_write(void *dst, const void *src, size_t size)
  60 {
  61         long copied;
  62
  63         while (size) {
  64                 copied = s390_kernel_write_odd(dst, src, size);
  65                 dst += copied;
  66                 src += copied;
  67                 size -= copied;
  68         }
  69 }
  70
  71 static int __memcpy_real(void *dest, void *src, size_t count)
  72 {
  73         register unsigned long _dest asm("2") = (unsigned long) dest;
  74         register unsigned long _len1 asm("3") = (unsigned long) count;
  75         register unsigned long _src  asm("4") = (unsigned long) src;
  76         register unsigned long _len2 asm("5") = (unsigned long) count;
  77         int rc = -EFAULT;
  78
  79         asm volatile (
  80                 "0:     mvcle   %1,%2,0x0\n"
  81                 "1:     jo      0b\n"
  82                 "       lhi     %0,0x0\n"
  83                 "2:\n"
  84                 EX_TABLE(1b,2b)
  85                 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
  86                   "+d" (_len2), "=m" (*((long *) dest))
  87                 : "m" (*((long *) src))
  88                 : "cc", "memory");
  89         return rc;
  90 }
  91
  92 static unsigned long _memcpy_real(unsigned long dest, unsigned long src,
  93                                   unsigned long count)
  94 {
  95         int irqs_disabled, rc;
  96         unsigned long flags;
  97
  98         if (!count)
  99                 return 0;
 100         flags = __arch_local_irq_stnsm(0xf8UL);
 101         irqs_disabled = arch_irqs_disabled_flags(flags);
 102         if (!irqs_disabled)
 103                 trace_hardirqs_off();
 104         rc = __memcpy_real((void *) dest, (void *) src, (size_t) count);
 105         if (!irqs_disabled)
 106                 trace_hardirqs_on();
 107         __arch_local_irq_ssm(flags);
 108         return rc;
 109 }
 110
 111 /*
 112  * Copy memory in real mode (kernel to kernel)
 113  */
 114 int memcpy_real(void *dest, void *src, size_t count)
 115 {
 116         if (S390_lowcore.nodat_stack != 0)
 117                 return CALL_ON_STACK(_memcpy_real, S390_lowcore.nodat_stack,
 118                                      3, dest, src, count);
 119         /*
 120          * This is a really early memcpy_real call, the stacks are
 121          * not set up yet. Just call _memcpy_real on the early boot
 122          * stack
 123          */
 124         return _memcpy_real((unsigned long) dest,(unsigned long) src,
 125                             (unsigned long) count);
 126 }
 127
 128 /*
 129  * Copy memory in absolute mode (kernel to kernel)
 130  */
 131 void memcpy_absolute(void *dest, void *src, size_t count)
 132 {
 133         unsigned long cr0, flags, prefix;
 134
 135         flags = arch_local_irq_save();
 136         __ctl_store(cr0, 0, 0);
 137         __ctl_clear_bit(0, 28); /* disable lowcore protection */
 138         prefix = store_prefix();
 139         if (prefix) {
 140                 local_mcck_disable();
 141                 set_prefix(0);
 142                 memcpy(dest, src, count);
 143                 set_prefix(prefix);
 144                 local_mcck_enable();
 145         } else {
 146                 memcpy(dest, src, count);
 147         }
 148         __ctl_load(cr0, 0, 0);
 149         arch_local_irq_restore(flags);
 150 }
 151
 152 /*
 153  * Copy memory from kernel (real) to user (virtual)
 154  */
 155 int copy_to_user_real(void __user *dest, void *src, unsigned long count)
 156 {
 157         int offs = 0, size, rc;
 158         char *buf;
 159
 160         buf = (char *) __get_free_page(GFP_KERNEL);
 161         if (!buf)
 162                 return -ENOMEM;
 163         rc = -EFAULT;
 164         while (offs < count) {
 165                 size = min(PAGE_SIZE, count - offs);
 166                 if (memcpy_real(buf, src + offs, size))
 167                         goto out;
 168                 if (copy_to_user(dest + offs, buf, size))
 169                         goto out;
 170                 offs += size;
 171         }
 172         rc = 0;
 173 out:
 174         free_page((unsigned long) buf);
 175         return rc;
 176 }
 177
 178 /*
 179  * Check if physical address is within prefix or zero page
 180  */
 181 static int is_swapped(unsigned long addr)
 182 {
 183         unsigned long lc;
 184         int cpu;
 185
 186         if (addr < sizeof(struct lowcore))
 187                 return 1;
 188         for_each_online_cpu(cpu) {
 189                 lc = (unsigned long) lowcore_ptr[cpu];
 190                 if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc)
 191                         continue;
 192                 return 1;
 193         }
 194         return 0;
 195 }
 196
 197 /*
 198  * Convert a physical pointer for /dev/mem access
 199  *
 200  * For swapped prefix pages a new buffer is returned that contains a copy of
 201  * the absolute memory. The buffer size is maximum one page large.
 202  */
 203 void *xlate_dev_mem_ptr(phys_addr_t addr)
 204 {
 205         void *bounce = (void *) addr;
 206         unsigned long size;
 207
 208         get_online_cpus();
 209         preempt_disable();
 210         if (is_swapped(addr)) {
 211                 size = PAGE_SIZE - (addr & ~PAGE_MASK);
 212                 bounce = (void *) __get_free_page(GFP_ATOMIC);
 213                 if (bounce)
 214                         memcpy_absolute(bounce, (void *) addr, size);
 215         }
 216         preempt_enable();
 217         put_online_cpus();
 218         return bounce;
 219 }
 220
 221 /*
 222  * Free converted buffer for /dev/mem access (if necessary)
 223  */
 224 void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf)
 225 {
 226         if ((void *) addr != buf)
 227                 free_page((unsigned long) buf);
 228 }